This section provides background information related to the present disclosure which is not necessarily prior art. This section also provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
Optical microscopy is the gold standard for the visualization of biological entities as well for the identification, diagnosis and monitoring of many diseases such as sickle-cell disease, malaria, and tuberculosis. High-end optical systems that achieve submicron resolution imaging rely on multi-element objective lenses that are expensive and bulky.
Biological imaging systems consist, in a broad sense, of a microscope for magnifying the section of the sample, a light source to illuminate the sample, and a camera which can be attached to the eyepiece of the microscope to take digital or analog images of the section of the sample which is being observed. For most applications, resolutions on the order of one micron or better are needed for observing fine details of the sample as well as for carrying out tasks such as counting of cells within a given sample volume. This is normally achieved by employing expensive high magnification immersion objectives for the microscopes, which can cost several thousand dollars each.
The large physical size of many microscopes is an impediment to making measurements in controlled environments, such as incubators or with living laboratory animals, such as mice, rats or guinea pigs.
Stereoscopes normally have a single optical train of lenses, prisms, and mirrors for collecting the light from the sample and forming an image at the image plane or the eye of the observer. Single train nature of the microscope combined with a high-resolution, high numerical aperture requirement results in immersion objectives which have very narrow fields of view that limit the observation area to about a hundred microns in diameter. This limitation prevents simultaneous observation of a large area of the sample with high resolution. To observe other parts of the sample, the sample has to be physically moved and brought into focus again.
Ball lenses have been used in optics for laser collimating, fiber coupling, and endoscopic imaging. Lately, ball lenses have been used to constructing miniaturized microscopes. However, the resolution and image quality of the previous attempt at making simple imaging systems with ball lenses was not very successful—maximum resolution achieved was greater than one micron and the image quality was poor due to its construction.
Miniature microscope lenses were made by essentially miniaturizing the microscope objectives (U.S. Pat. No. 7,023,622). Arrays of these miniaturized objective lenses were used to make scanning array microscope systems. However, the cost of these systems was prohibitively high.
The present teachings address the shortcomings of the prior art, providing a novel and inexpensive imaging system, which costs at least an order of magnitude less and is smaller by a similar amount while providing as high a resolution as the best immersion microscope objectives.
According to the principles of the present teachings, a compact lens system is provided for imaging a sample in some embodiments. The compact lens system comprises a substrate having a well formed therein, the well having an open first end and an open second end wherein the second end opposing the first end and being in communication therewith. The system further comprises a lower transparent member extending along a lower surface of the substrate, thereby enclosing the open second end of the well, and an index matching material disposed in the well. A lens member is disposed in the well and in optical contact with the index matching material disposed in the well. A refractive index of said lens member being generally equal to a refractive index of said index matching material. A spacer member extends from at least one of the substrate and the lower transparent member to define a spacing from a focal point of the lens member, wherein the lens member and the index matching material cooperate to image a sample disposed below the lower transparent member.
In some embodiments, a compact lens array system for imaging a sample is provided. The compact lens array system comprises a substrate having a plurality of microwells disposed in an array of rows and columns, each of the microwells having an open first end and an open second end. The second end opposing the first end and being in communication therewith. A lower transparent member extends along a lower surface of the substrate enclosing the open second end of each of the microwells. A reservoir is provided and a microfluidic channel fluidly couples at least one row of the array of microwells to the reservoir. An index matching material is disposed in the reservoir and in fluid communication with the at least one row of the array of microwells via the microfluidic channel. A plurality of lens members are disposed in each of the microwells in optical contact with the index matching material disposed in the microwells. A refractive index of each of the plurality of the lens members is generally equal to a refractive index of the index matching material. A spacer member extends from at least one of the substrate and the lower transparent member to define a spacing from a focal point of the plurality of lens members, wherein the lens members and the index matching material cooperate to image a sample disposed below the lower transparent member.
In some embodiments of the present teachings, a novel microfluidic-based device is provided for obtaining a low-cost, high-NA array of miniaturized ball lenses for imaging biological samples. In some embodiments, lenses are made of high index of refraction material. The lenses can be placed on top of an array of liquid-filled lens wells that are microfabricated as a holder platform. The precise platform configuration enables easy assembly and effective holding/retention. Moreover, the Microfluidic-based Oil-Immersion (μOIL) lens array or chip of the present teachings provides optical performance (resolution, NA) equivalent to the performance of a conventional microscope objective, while also enabling multiple wide field of view imaging as its size can be easily scaled up. A low-cost, compact, high-resolution, high numerical aperture optical imaging system using the compact lens system for counting cells is provided.
The present teachings, in some embodiments, employ single ball lens optics to overcome the cost and complexity issues associated with compound lens microscope objectives. Higher numerical aperture and submicron resolution is achieved by using semiconductor manufacturing techniques to make a microfluidic lens holder which simultaneously positions the lens at a precise distance from the sample and immerses half of the ball lens, for example, in an index matching fluid effectively creating an immersion microscope objective with resolution comparable to the best compound microscope objectives. By having an array of miniball lenses, it is possible to simultaneously image many different samples with equal resolution simultaneously or image different parts of a large sample with high resolution. A sample cartridge is inserted between the illumination source and the lens array. In some embodiments, an LED light source, wavelength filters and imaging sensor can be used to enable both bright field and fluorescence imaging.
In some embodiments, the imaging sensor located in the image plane of the mini ball lenses records digitally all of the images formed by the mini lenses simultaneously with approaching the diffraction limit. The advantages of such a system is obvious to those skilled in the art: By way of non-limiting example, it is possible to follow different events taking place at the cellular or subcellular level, to count red and white blood cells or their subpopulations with good statistics, observe response of cells to different drugs, record time dependent changes occurring in cells exposed to different environments, observe growth of different embryos, white and red blood cell counting and many similar phenomena too many to list here. Furthermore, the small size and weight of the compact lens system, around one cubic inch in some embodiments, allows its use in remotely monitoring samples where large bulky microscopes cannot be used.
The compact lens system of the present teachings can be part of a lab-on-chip system or it can be used as an add-on module in low cost stereoscopes to enable high resolution imaging of small objects in the lab, in the doctor's office, or in the field. The compact lens system can be integrated to a CMOS (complementary metal oxide semiconductor) commercial sensor for a miniature wireless microscope system to monitor biological development in an incubator, a compact imaging system for cell counters, or can be used as an optical part of Digital Pathology Scanner.
The present teachings provide a number of advantages, including providing an array of mini objectives which give multiple field of views whereas expensive bench top microscopes can only see one field of view, only one objective at a time. Moreover, each objective mini-lens of the present teachings provides high numerical aperture and high resolution (˜0.5 microns) and an inexpensive and small foot print lens holder. This lens array chip is 1*1*0.2 cm3 volume, which make it easy to integrate into a compact & light weight imaging system. Furthermore, the present teachings can be used in a wide range of optical imaging applications, such as Cell Counters, Point of Care Diagnostic systems, Miniature microscope systems that can be used in incubators, and high resolution Digital Pathology Scanners.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.